The 20-year-old model - who is known for covering Sports Illustrated twice in her short career - was shown a picture of his band One Direction, and picked the 18-year-old singer out as the cutest member of the British boy band.
Next month, the pair will be meeting when they both attend the MTV Video Music Awards in September.
Harry - who has previously dated TV presenter Caroline Flack, 32 - may be interested in reciprocating his feelings as he is known to be a fan of older women.
A source told The Sun newspaper: "He may like older women but Kate's in a different league."
However, there may be some stiff competition for Kate, as Harry was recently found to have swapped numbers with Canadian singer Alyssa Reid when they both performed at the Liverpool Echo Arena in the UK.
Alyssa - who later posted a picture of herself with Harry and his bandmate Zayn Malik, who has a girlfriend, on twitter - said: "Yes I have introduced myself and I may or may not have got a phone number. I never kiss and tell. I'm not telling you. I can't tell.
"I would never go for a taken man though, so he must be one of the single ones."